Oven and method of operating the same

ABSTRACT

The invention in particular relates to an oven ( 1 ) for baking food products ( 3 ). In order to improve automated heating procedures, the oven ( 1 ) comprises a camera ( 7 ) and a distance sensor ( 8 ), for example, which are used in concert to enable precise extraction of product-features that are relevant and used with automated heating procedures.

The present invention relates to an oven and to a method of operatingthe same.

Operating state of the art baking ovens usually requires a user toselect temperature and duration, and more or less continuously toobserve the time course of a baking process.

In order to ease the operation of ovens, methods have been developed formore or less automating baking processes. Such methods for exampleprovide automatic temperature control based on surface or coretemperature values measured by temperature sensors during the bakingprocess. Other known methods numerically approximate actual temperaturesduring the baking process, based on the applied temperature and the heatequation, for example.

In the field of baking ovens, and more particularly in the field ofmicrowave ovens, it is known to use ultrasonic or infrared distancesensors, or photo sensors to determine a position, shape or status ofthe product, e. g. frozen, chilled or thawn. Position, shape and statusare used for controlling the process of heating the product.

Other methods use cameras for taking pictures of the product and forapproximating the shape, volume or size of the product in order toimprove automation of the heating process.

The known methods and related ovens are far from providing possibilitiesof fully automated heating, and often require user interaction. In thetechnical field of ovens, it is therefore desirable to provide enhancedand user friendly possibilities for automated operation of ovens.

Therefore, it is an object of the invention to provide an oven suitablefor more accurately conducting a heating process in an automated manner.It is a further object to provide a method of more accurately operatingan oven in an automated manner.

This object is achieved by an oven and a method of operating the sameaccording to claims 1 and 8, respectively. Advantageous embodimentsresult from dependent claims 2 to 7 and 9 to 14.

According to a first aspect of the present invention, an oven forheating food products, comprising a chamber adapted to receive theproduct via a chamber opening is provided. The oven can be of any typesuitable for heating products, particularly food products. Heating ofthe products can comprise baking, broiling, browning, roasting orthawing and the like. The oven preferably is a baking oven, but can beof any other type, for example a microwave oven.

The oven according to the invention comprises a product-featureextracting system designed for extracting at least one product-featurerepresentative of a configuration of the product. Without making a claimto be exhaustive, possible product-features are: vertical cross section,horizontal cross section, shape, particularly 3d-model, surface, surfacearea, volume, dimensions, particularly length, width, height of theproduct, center-of-gravity of the product and center-of-gravity tosurface distance

The product-feature extracting system comprises at least one camera, e.g. a digital camera, designed and positioned for recording producttop-views. A product top-view shall mean any view of the product, e. g.a two-dimensional picture of the product, showing at least a part of theupper side of the product. Here, the upper side of the product shallmean a side of the product facing upwards in a position occupied in thecourse of being heated within the chamber.

The term “product top-view” shall not preclude sections or elements ofan object inserted along with the product into the chamber being part ofthe view. Such an object can be a tray, for example, carrying theproduct. Other objects are conceivable, for example temperature sensorsattached to or put into the product. In order to ease differentiationbetween product and object within a view, special marks, colors or colorcodes can be provided with the object for example.

The product-feature extracting system further comprises at least onecontour-level unit designed and positioned for extracting orhighlighting contour-levels of at least a section of the product and, asthe case may be, an object intended for insertion along with the productinto the chamber.

Further, the product-feature extracting system comprises aproduct-feature extracting unit for extracting the at least oneproduct-feature on the basis of the top-views and contour-levels.

It shall be mentioned, that the invention is not restricted to onesingle product and one single object. Of course, the invention alsoapplies to more than one product and more than one object, respectively.

The provision and utilization of product top-views and contour-levelsmakes it possible to extract the product feature or product featuresmore accurately. More accurate product features, such as shape, volumeand the like, are the basis for conducting automated heating processesmore accurately. In particular, automated heating processes can beconducted with minimal or even without any user interaction.

A mounting position of at least one of the at least one camera and theat least one contour-level unit preferably is such that high quality andaccurate views and contour-levels can be obtained for a wide range ofproduct types, product shapes and product locations within the chamber.Preferred mounting positions are: upper part of the opening, preferablyat the entrance site, above a door for closing and releasing theopening, upper part of the chamber, preferably halfway the depth of thechamber. Mounting positions outside the chamber, e. g. at the entrancesite, or above the door have the advantage of greatly avoidingdisturbing and harmful influences arising from high temperatures andtemperature variations, dirt that could probably stain the camera lens,humidity and infrared radiation reflected by the product, object orchamber walls.

Particularly mounting positions outside the chamber, open thepossibility to obtain the product top-views and contour-levels in thecourse of inserting the product and object into the chamber. A mountingposition at an upper part of the chamber, about halfway the depth of thechamber, opens the possibility of acquiring additional product top-viewsand contour-levels in the course of heating the product. Such additionalproduct top-views and contour-levels may be used to further optimizeautomated heating of the product. For example, the respective status ofbrowning, or shape variations of the product can be extracted andmonitored during heating. Such and other parameters are often indicativeof the stage of the heating process.

The contour-level unit can comprise at least one of a distance sensordesigned for measuring distances between the sensor and upper surfacelevels of the product and the object, respectively, and a light emittingdevice, preferably a laser, more preferably a line laser, positioned anddesigned for highlighting a contour of the product and object,respectively, by respectively projecting a beam of light, preferably alaser line, preferably at a predefined angle, onto the product andobject. The beam of light may comprise at least one of at least one ray,at least one fan-shaped beam of light and at least one cone-shaped beamof light. Thereby it is possible to highlight single pointcontour-levels, one or several contour-level slices or one or severalcontour-level spots. Note, that aperture angles of the beam of light, asfar as relevant, may be used for calculating contours of height levelsof the product and object, respectively.

Comparatively robust and reliable distance sensors, such as infrared orultrasonic distance sensors can be used for measuring the distancesbetween the product and the sensor. The distances can be measured in thecourse of inserting the product into the oven. Such distances arerepresentative of contour-levels of the product and can be correlatedwith the top-view or with several top-views to calculate aproduct-feature, as for example a cross-sectional contour, the volume, ashape of the product or height levels of the product.

As mentioned above, not only distance sensors, but also light emittingdevices or even distance sensors together with light emitting devicescan be used in concert with one or more cameras to extract productfeatures. The light emitting device, laser and line laser, respectively,can be used to project a beam of light or laser line onto the productand object, respectively, thereby highlighting contour-levels of atleast a section of the product or object. By using light emittingdevices emitting a green or red beam of light, for example, thehighlighted contour-levels or even a section of the product contour canbe extracted from the product top-view using image processing methods,for example.

Highlighted contour levels can be identified within the producttop-views on the basis of special or characteristic colors or grayscales of the beam of light or laser line, respectively. Similarly,contour-levels obtained by using a light emitting device and producttop-views can be combined to calculate at least one product-feature. Aplurality of product top-views containing highlighted contour-levels canbe recorded in the course of inserting the product into the chamber,which product views can be combined to accurately calculate the requiredproduct-feature. It shall be mentioned, that triangulation can be usedto calculate contour-levels, if for example the starting point andirradiation angle of the beam of light, or laser line, respectively, isknown. However, other methods can be used as well.

Automated heating of the product can conducted more accurately, if aninitial temperature of the product, i. e. a temperature of the productprior to heating, is known. The initial temperature may for example beused to select a predefined heating protocol from a list of givenheating protocols.

The initial temperature and the product-feature “surface area”, forexample, can be used for estimating, calculating or predicting energyconsumption of the product during heating.

Further, the initial temperature or temperature distribution can be usedto classify the product as frozen, chilled or non-frozen, for example.

Therefore it is of advantage, if the oven further comprises at least onetemperature sensor adapted to measure at least one of an initialtemperature and initial temperature distribution of the product. Theterm “initial temperature” shall mean the temperature prior to heating.Such a temperature sensor may be of infrared type. Note, that automaticheating can be further refined by using temperature values measuredduring heating.

In order to reduce impacts arising from heating the product,particularly in the case of baking ovens reaching chamber temperaturesof 200° C. and more, it can be of advantage, if the temperature sensoris mounted outside the chamber.

However, robust temperature sensors can be used and mounted within thechamber or a wall thereof. Such positions make it possible to trace theproduct temperature during heating, which can be used to optimizeautomated heating, as already mentioned above.

Particularly in connection with baking ovens, it has turned out, thatsensors mounted outside the chamber at an upper site or above theopening make it possible to measure the initial temperature or otherparameters in nearly any circumstances and for nearly any product types.This is due to the fact, that the top side of a product rarely is hiddenor covered during insertion and therefore is nearly always accessible torespective measurements. However, any other suitable mounting positionsare possible.

Depending on the position of the temperature sensor, the initialtemperature or temperature distribution can be measured at least one ofprior to, in the course of and after insertion of the product into thechamber. It is of advantage, if the time point of initial temperaturemeasurement is close to a starting point of the heating procedure.

A further important parameter in connection with automated heating isthe product weight. Therefore it is of advantage if the oven furthercomprises at least one weight sensor for at least one of measuring anddetermining the weight of the product and object, respectively.

If the weight of the object, for example a tray, is known, the netweight of the product can be calculated. The weight can be used tocalculate the density of the product if the product-feature “volume” ofthe product is known or calculated beforehand.

The weight sensor also can be used to determine a time coursedevelopment of the product weight during heating. The time course of theproduct weight can be used for further refining automated heating.

It shall be mentioned, that it is also possible that the oven has afunction of inputting the weight by a user.

The oven according to invention makes it possible to implement reliableand precise methods of operating the oven in an automated manner. Amethod of operating the oven is provided in a second aspect of theinvention.

The method comprises the following steps:

a) extracting a product-feature of the product intended to be heated inthe chamber, by

-   -   recording at least one product top-view via the at least one        camera;    -   at least one of extracting or highlighting contour-levels of at        least a section of the product and, as the case may be, an        object intended for insertion along with the product into the        chamber, by using at least one contour-level unit; and    -   extracting the at least one product-feature on the basis of the        top-views and contour-levels and        b) based on at least one product-feature, and optional secondary        data representative of a physical configuration of the product,        preferably at least one of product temperature, product weight        and product density, automatically controlling or conducting        heating of the product.

Reference is made to the explanations in connection with the firstaspect of the invention. Hence the method according to the second aspectprovides the possibility of conducting automated heating of the productin a particularly precise, accurate and reliable manner.

Product top-views, contour-lines, product-features, secondary data andthe like can be obtained as mentioned further above. Hence reference ismade to respective explanations in connection with the first aspect ofthe invention.

For extracting certain product-features it may be of advantage, if atleast a section of the product is registered within a two-dimensionalproduct top-view, preferably recorded at a time the product iscompletely in a field of view of the camera. Such registration may beuseful to identify the product in the respective view. Registrationresults may be used to calculate edges, borders or circumferential linesof the product. Additional data retrieved from registration, i. e.registered product data such as a length or diameter of the product, canbe used for calculating a certain product feature.

In the case that contour-levels of only a portion of the product andobject, respectively, are available, additional contour-levels can beapproximated on the basis of available contour-levels. The additionalcontour-levels facilitate product-feature extraction.

The situation of a limited number of contour-levels may arise fromlimited field of views and detection ranges, which, by the way, may beintentional. Further, unfavourable product positions also may lead to alimited number of contour-levels.

Similarly, if only a section of the product can be registered in theproduct top-views, reconstruction of the whole product can be based onat least one of presumptions related to product shape, as for examplesymmetry, contour-levels and further approximated contour levels. Inaddition, registration data of only a section of the product can becompared to product shapes or forms that are typical to respective ovensand related methods. Here, a database of typical product shapes can beused.

In many instances, the object is a tray or plate on which the product isplaced and rests during heating. Contours, particularly cross-sectionalcontours of the product, can be extracted more easily, if a tray-levelor plate-level, i. e. a height level the tray or plate occupies withinthe chamber is determined automatically. This can be done on the basisof tray or plate contour-levels, i. e. contour-levels identified tobelong to the tray or plate as such. This also applies to situations, inwhich several objects are inserted in concert with the product. Forexample, the product can be positioned on or in a plate, cup or bakingtin which in turn can be placed on a tray. A priori knowledge of therespective object or objects, such as weight, height, height-level andthe like can be used for product-feature extraction. It shall bementioned, that the tray-level usually is limited to a given number ofpossible tray-levels.

The invention will be described in further detail with reference to thedrawings, in which

FIG. 1 illustrates a schematic sectional side view of a baking oven in afirst embodiment;

FIGS. 2 to 4 illustrate schematic sectional side views at different timepoints in the course of inserting a tray along with a food product intoa baking chamber of the baking oven;

FIG. 5 illustrates a product top-view;

FIG. 6 illustrates a diagram of distances measured by a distance sensor;

FIG. 7 illustrates a schematic sectional side view of a baking oven insecond embodiment;

FIG. 8 illustrates a product top-view including high-lighted contourlevels;

FIG. 9 illustrates laser line projections representative of highlightedcontour-levels;

It shall be noted, that like reference numbers denote like elements, orelements that are similar or similar in function. The Figures areschematic and not necessarily true to scale. The invention will bedescribed in connection with a baking oven, which shall not be construedas limiting the scope of invention. The function of the baking oven isdescribed only in so far as is necessary for understanding theinvention.

FIG. 1 illustrates a sectional side view of a baking oven 1 in a firstembodiment. The baking oven 1 comprises a baking chamber 2. The chamber2 is adapted to receive a baking product 3 positioned on a tray 4 via achamber opening 5. The baking oven 1 further comprises a door 6 adaptedfor closing and releasing the opening 5, which is indicated by a doublearrow. FIG. 1 shows the situation prior to insertion of the food product3.

The baking oven further comprises a digital camera 7 and a distancesensor 8 of infrared or ultrasound type. Infrared waves or ultrasoundwaves used for distance measurement are indicated by a broken line anddesignated by reference number 9.

In the present case, the distance sensor 8 is mounted at an entrancesite of the chamber opening 5, above the door 6 in a closed positionthereof. In such a position the distance sensor 8 can be shielded fromheat, humidity and dust generated in the course of baking the bakingproduct 3. Consequently, the distance sensor 8 is not exposed toinfluences that may disrupt distance measurements.

The digital camera 7 is mounted in an upper part of the chamber opening5 about halfway the depth of the baking chamber 2. Such a position hasthe advantage, that product top-views can be recorded for a wide varietyof baking product positions within the baking chamber 2. Further,product top-views can be recorded in the course of baking.

An operational mode of the baking oven 1 will be described in connectionwith FIGS. 2 to 4 illustrating sectional side views of the baking oven 1at different points in time in the course of inserting the tray 4 alongwith the baking product 3 into the baking chamber 2.

The distance sensor 8 can be activated to start distance measurementsvia signals representative of a state of the door 6, for example. Suchsignals may indicate, for example, that the door 6 is open or in theclosed state, and can be used to activate and deactivate the distancesensor 8, respectively. Other signals, such as signals of motion andcontact sensors scanning the entrance site of the baking chamber 2 forobjects to be inserted into the baking chamber 2, can also be used. Ifsuch a sensor detects an object to be inserted, the distance sensor 8can be activated to start distance measurements.

In the present case, the distance sensor 8 is activated upon opening thedoor 6, which has already occurred with the situation in FIG. 1. Afteractivation, the distance sensor 8 continuously measures distances in thecourse of insertion of the food product 3 and tray 4 into the bakingchamber 2. The distances are representative of distances between thedistance sensor 8 and a bottom 10 of the baking chamber 2, between thedistance sensor 8 and the tray 4 or between the distance sensor 8 andthe baking product 3.

In FIG. 2, a part of the tray 4, but not the baking product 3, hasalready passed the distance sensor 8. Distances measured up to thisstage are representative of a tray-level, i. e. a height level of thetray 4 relative to the bottom 10 of the baking chamber 2. A prioriinformation about possible tray-levels may be used for tray-leveldetermination, if for example height levels of tray guides of the sidewalls of the baking chamber 2 are known.

Upon further insertion of the tray 4 also the baking product 3 will passthe distance sensor 8. Distances measured in this stage, arerepresentative of local height levels of the baking product 3. In FIG.3, about half of the baking product has passed the distance sensor 8.

In FIG. 4, the tray 4 and baking product 3 are completely inserted intothe baking chamber 2, and the baking product 3 is in its final position,ready for baking. In this stage, a product top-view is recorded by thedigital camera 7, which is indicated by broken lines.

FIG. 5 illustrates an exemplary product top-view 11. The producttop-view 11 in the present case is a 2-dimensional picture showing thebaking product 3 and portions of the tray 3 which, related to an upperpoint of view, are not hidden by the baking product 3. The contents ofthe product top-view 11 may vary from case to case and are dependent onthe field of view of the camera 7. The field of view, and hence thecontent of information of the product top-view 11, may be adapted torespective requirements.

The camera 7 may be of color or monochrome type. The product top-view 11is analysed using conventional image processing methods, to register thebaking product 3. Depending on the type of camera 7, either colors orgrey scales can be used for registration of the baking product 3. As aresult of registration a border 12 between the baking product 3 and thetray 4 can be obtained. The border 12 can be converted into coordinates,for example Cartesian x-y-coordinates.

FIG. 6 illustrates a diagram of distances d measured by the distancesensor 8 in the course of tray insertion. The distances d are given inarbitrary units (axis of ordinates) according to their chronologicalsuccession (abscissa), denoted by reference sign n.

As can be seen from FIG. 6, the distances d can be classified in firstdistances d1 between the distance sensor 8 and the bottom 10 of thebaking chamber 2, second distances d2 between the distance sensor 8 andthe tray 4 and third distances d3 between the distance sensor 8 and thebaking product 3.

In particular, the distances d are representative of contour-levels ofthe baking product 3 and tray 4. A contour-level unit (not shown), asfor example a microelectronic component, can be used to extractcontour-levels from the distances d. For example, contour-levelsrepresenting a height profile of a cross-sectional contour of the bakingproduct 3 can be extracted by subtracting distance d2 representing thetray-level from each distance d3. The tray-level can be extracted byusing the product top-view and registration data, e. g. the border, toidentify sections of the tray 4 not hidden by the baking product 3. Thedistances d, i. e. the second distances d2 can then be assigned to therespective section. Alternatively, discontinuous rising or falling edgesin the succession of distances d, e. g. from bottom-level to tray-levelor from tray-level to bottom-level, can be used to identify thetray-level. All this can be done in an automatic manner without the needfor user interaction.

to A product-feature extracting unit (not shown), integral part of themicroelectronic component for example, can be used to combine the bakingproduct contour-levels with x-y-coordinates of the border 12 and tocalculate vectors suitable for extracting at least one of the surfaceand volume of the baking product 3. If required, further or otherproduct-features than the ones mentioned beforehand can be extracted.

In the present case, only contour-levels corresponding to a single crosssection of the baking product 3 are extracted. In order to calculate thesurface and volume from the contour-levels it is presumed that bakingproduct 3 is of symmetric shape. In order to extract theproduct-features more accurately, it is possible to compare thebaking-product 3 to a database of conventional product shapes, based onthe product top-view and available contour-levels. Alternatively, it ispossible to provide a user interface for inputting product shapeinformation suitable for extracting the product-feature in more detail.Further, it is possible to use several distance sensors 8 in order toextract contour-levels corresponding to different cross sectionalcontours or slices of the baking product. Likewise, several cameras canbe used. By using more than one distance sensor 8 and camera 7,respectively, it is possible to handle non-symmetric product shapes andeven cases, in which several baking products 3 are positioned on thetray 4.

It shall be mentioned, that additional contour-levels can beapproximated from contour-levels extracted as mentioned above, forexample by interpolation or extrapolation.

Based on the extracted product-features, it is possible to controlbaking of the baking product 4 in an automatic manner. Surface andvolume are decisive for heat consumption during baking. Hence, using atleast the aforementioned product-features gives rise to precise andenhanced automated baking processes.

Generally, a baking protocol selectable from a predefined list of commonbaking routines can serve as a basis for the automated baking process.Such a baking protocol may be selected on the basis of a product-featureor other configuration of the baking product 3.

For further enhancing automated baking, it is possible to make use ofsecondary data representative of a physical configuration of the bakingproduct 3. Secondary data such as product temperature, particularlyinitial product temperature, product weight and product density can beused. For determining the product temperature and product weight,further sensors such as temperature sensors and weight sensors,respectively, can be used. A temperature sensor may for example be usedto determine the baking-product configuration such as frozen, chilled,fresh or thawn and the like.

It shall be mentioned, that it is also possible to arrange the distancesensor 8 remote from the entrance site of the baking chamber 2. Thetemperature senor 8 can be arranged in the vicinity or besides thecamera 7. In this case, distances d of only a section of the bakingproduct 3 can be measured. If for example distances d of only one halfof the baking product 3 can be measured, product-features can beextracted on the assumption of symmetrical height of the baking product3. Note that there is the possibility to refine such generalpresumptions using information retrieved from product top-views.

However, with the aforementioned situation, i. e. positioning thedistance sensor 8 besides the camera 7, it is more involved to correlatemeasured distances d with the baking product 3.

This may be due to the fact that distance measurement may continue whilethe tray 4 and baking product 3 have reached their final position withinthe baking chamber 2. Therefore it is required to obtain the distance dmeasured at the end-point of insertion.

In order to obtain the distance d at the end-point, a sensor forgenerating a signal representative of an end-point of insertion could beused. This signal can be used either to stop distance measurements or tolabel the distance d measured at the end-point.

Alternatively, the distance d at the end-point can be determinednumerically.

Presumed, the speed of insertion is more or less constant, which formost cases indeed applies, the distance d at the end-point can becalculated, at least in good approximation, as follows:

Distance values belonging to the section of the tray 4, which is closeto the back wall of the baking chamber 2, not covered by the bakingproduct 3 and which section has passed the distance sensor 8 in thecourse of insertion can be determined. This can be done by using theresult of automatic tray-level recognition and registration of the foodproduct 3, in that distances d along linear tray section path between aninitial tray-level distance and the border 12 of the baking product 3are determined and assigned to the mentioned section of the tray 4. Thementioned section of the tray 4 can also be identified in a digitalproduct top-view by registration methods, for example.

After identifying this section or tray section path and relateddistances, the number of pixels of the section along the tray sectionpath can be determined. Note that the path along which distancemeasurements are conducted can be determined by using a-prioriinformation about the relative distance between camera 7 and distancesensor 8 and their respective product specifications, as for examplefield of view of the camera 7 and position of a sensor head of thedistance sensor 8.

Knowing the number of pixels and distances d corresponding to the traysection path, the ratio: number of distances per pixel can be calculatedfor the tray section path. As the insertion speed is assumed to beconstant, the calculated ratio shall also apply to the baking product 3and related distances.

After extracting the number of baking product pixels belonging to abaking product path immediately succeeding the tray section path, whichcan be done by using the registered border 12 and the pixel position ofthe distance sensor 8 or distance sensor head, the effective number ofdistances d belonging to the baking product path can be calculated andredundant distances can be discarded, leaving only relevant distances.Using the product top-view and all relevant distances, product featuressuch as surface of volume can be extracted. Note, that under theassumption that the baking product is symmetric, the relevant distancescan be mirrored, for example, or generally speaking assigned torespective symmetric locations.

FIG. 7 illustrates a schematic sectional side view of a baking oven in asecond embodiment. The following description is restricted todifferences compared to the first embodiment. As far as applicable, allfeatures mentioned in connection with the first embodiment shall applyto the second embodiment as well.

In the second embodiment, a line laser 13 is used instead of thedistance sensor. Note, that more than one line laser 13 or a combinationof line laser/s 13 and distance sensor/s 8 is also possible, which askilled person shall be able to implement, based on preceding andfollowing explanations.

The line laser 13 is positioned at the upper side of the chamber opening5 and preferably inclined by a predefined angle. The camera 7 also ispositioned at the upper side of the chamber opening 5, near the linelaser 13.

During insertion, the line laser 13 emits a green, fan-shaped laser line14 while the camera 7 continuously records product top-views 11. Notethat the laser line 14 may be of any other suitable color. In thepresent case, the camera 7 is of color type.

The laser line 14 strikes the baking product 3 and thereby highlightscontour-levels of the baking product 3. This is illustrated in FIG. 8.Note that only for the sake of simplicity of illustration, the bakingproduct 3 is chosen to be of square shape.

FIG. 8 illustrates a product top-view including contour levelshighlighted by the laser line 14. The green color of the laser line 14is distinguishable from most baking products 3 and colors used for trays4 and inner walls of baking chambers 2. Therefore, laser lineprojections representative of highlighted contour levels can beextracted in each of the product top-views 11. Due to the inclination ofthe line laser 13, the laser line projections are staggered in theproduct top-views. Note that the field of view of the camera 7 at thebottom 10 of the baking chamber 2 is indicated by a broken-dotted line,and denoted by reference number 15.

FIG. 9 illustrates the laser line projections of FIG. 8 after extractionfrom the respective product top-view 11. The original size of therecorded product top-view 11 is indicated by a frame. The laser lineprojections can be classified as follows: first projections p1representative contour levels of the bottom 10 of the baking chamber 2,second laser line projections p2 representative of contour levels of thetray 4 and third laser line projections p3 representative of contourlevels of the baking product 3.

Based on the laser line projections p1, p2 and p3, the local contourlevel, i. e. the relative height of a respective location, i. e. bottom10, tray 4 and baking product 3, can be calculated. Using theinclination angle, the position of the line laser 13 and the distancesbetween respective laser line projections p1 to p3 and center line 16 ofthe field of view 15, respective contour levels can be extracted bytriangulation, for example.

A product top-view containing the whole tray 4 and baking product 3 canbe used to register the baking product 3 in order to determine theborder 12. Using the pixel resolution of the camera 7, for example, theborder 12 can be transformed into x-y-coordinates, which coordinates canbe combined with extracted contour levels of the baking product 3, fordetermining surface and volume, or other product-features.

The advantage of using a line laser 13 according to the secondembodiment is, that all types of regular and irregular product shapesand situations in which several equal or different shaped bakingproducts 3 are positioned on the tray 4 can be handled withoutdifficulties.

The use of a linear, 1-dimensional laser line instead of the fan-shapedlaser line 14 of the second embodiment corresponds to the situation ofthe first embodiment, and reference is made to the first embodiment.

As to the second embodiment, advantages related to automation of thebaking process apply mutatis mutandis.

Although the invention has been described in connection with a bakingoven 1, the invention can be applied to other types of ovens, whereinall the advantages and advantageous effects can be achieved as well.

From the discussion above, it becomes clear that the object of theinvention is achieved by an oven and a method as set out in the claims.

LIST OF REFERENCE SIGNS

1 baking oven2 baking chamber3 baking product4 tray5 chamber opening6 door7 digital camera8 distance sensor9 infrared or ultrasound wave10 bottom11 product top-view12 border13 line laser14 laser line15 field of view16 center lined distanced1, d2, d3 first to third distancesn numberp1, p2, p3 first to third laser line projections

1. Oven (1) for heating food products (3), comprising a chamber (2) adapted to receive the product (3) via a chamber opening (5), and a product-feature extracting system designed for extracting at least one product-feature representative of a configuration of the product (3), the system comprising: at least one camera (7) designed and positioned for recording product top-views (11); and—at least one contour-level unit designed and positioned for extracting or highlighting contour-levels of at least a section of the product (4) and, as the case may be, an object (4) intended for insertion along with the product (3) into the chamber (2); and—a product-feature extracting unit for extracting the at least one product-feature on the basis of the product top-views (11) and contour-levels.
 2. Oven (1) according to claim 1, wherein a mounting position of at least one of the at least one camera (7) and the at least one contour-level unit is selected from the group consisting of: upper part of the opening (5), preferably at the entrance site, above a door (6) for closing and releasing the opening (5), upper part of the chamber (2), preferably halfway the depth of the chamber (2).
 3. Oven (1) according to claim 1, wherein the contour-level unit comprises at least one of a distance sensor (8) designed for measuring distances (d) between the sensor (8) and upper surface levels of the product (3) and the object (4), respectively, and at least one light emitting device, preferably at least one laser, more preferably at least one line laser (13), designed for highlighting a contour of the product (3) and object (4), respectively, by respectively projecting a beam of light, preferably a laser line (14), preferably at a predefined angle, onto the product (3) and object (4).
 4. Oven (1) according to claim 3, wherein at least one of the at least one distance sensors (8) is an infrared or ultrasonic distance sensor, and wherein at least one of the at least one light emitting devices is designed for emitting a red or green beam of light (14).
 5. Oven (1) according to claim 1, further comprising at least one temperature sensor, preferably an infrared temperature sensor, preferably mounted outside the chamber, preferably at an upper site of the opening, for measuring at least one of an initial temperature and initial temperature distribution of the product (3) and object (4), respectively.
 6. Oven (1) according to claim 1, further comprising a weight sensor for at least one of measuring and determining the weight of the product (3) and object (4), respectively.
 7. Oven (1) according claim 1, wherein the product-feature is selected from the group consisting of: vertical cross section, horizontal cross section, shape, particularly 3d-model, surface, surface area, volume, dimension, particularly length, height and width of the product (3), center-of-gravity of the product (3) and center-of-gravity to surface distance.
 8. Method of operating an oven (1) for heating a food product (3) comprising the steps of a) extracting a product-feature of a product (3) intended to be heated in a chamber (2) of the oven (1), by recording at least one product top-view (11) via at least one camera (7); at least one of extracting or highlighting contour-levels of at least a section of the product (3) and, as the case may be, an object (4) intended for insertion along with the product (3) into the chamber (2), by using at least one contour-level unit; and extracting the at least one product-feature on the basis of the top-views (11) and contour-levels and b) based on at least one product-feature, and optional secon-dary data representative of a physical configuration of the product (3), preferably at least one of product temperature, product weight and product density, automatically controlling or conducting heating of the product (3).
 9. Method according to claim 8, wherein at least a section of the product (3) is registered within a two-dimensional product top-view (11), and wherein the extraction of at least one product-feature is further based on registered product data, preferably edges, borders (12) or circumferential lines of the product (3).
 10. Method according to claim 8, wherein the step of extracting contour-levels comprises measuring distances (d, d1, d2, d3) between at least one distance sen-sor (8) and upper surface levels of the product (3) and the object (4), respectively, by means of the at least one distance sensor (8), preferably designed for measuring distances (d, d1, d2, d3) via infrared or ultrasonic waves.
 11. Method according to claim 8, wherein the step of highlighting contour-levels comprises highlighting a contour of the product (3) and object (4), respectively, by respectively projecting at least one beam of light, preferably a laser line (14), preferably at least one of green and red, and preferably at a predefined angle, onto the product (3) and object (4), respectively.
 12. Method according to claim 8, wherein further contour-levels for enhanced product-feature extrac-tion are approximated, preferably extrapolated or interpolated, on the basis of available contour-levels.
 13. Method according to claim 8, wherein the object is a tray (4) for placing the product (3) thereon, and wherein a tray-level is automatically determined on the basis of tray contour-levels.
 14. Method according to claim 8, wherein the product-feature is selected from the group consisting of: vertical cross section, horizontal cross section, shape, particularly 3d-model, surface, surface area, volume, dimen- sion, particularly length, height and width of the product (3), center-of-gravity of the product (3) and center-of-gravity to surface distance. 